Take a bunch of Comfrey and make organic plant food

When my Soapwort was looking sickly and needed a tonic, I knew just the thing to help restore it to a healthy state. It was time to give this plant a shot of my ‘magic potion’ for plants … or as some of you may know it, liquid Comfrey feed. Fortunately, I have some left over from last year so that has given the Soapwort a boost.

Sad and sickly Soapwort in need of a tonic

Comfrey is a substantial herb, growing about a metre (3 feet) tall, with hairy leaves and rather rough stems. The oval leaves are larger at the base, decreasing in size as they grow up the stem.

Russian Comfrey growing in undergrowth near allotment gardens — Russian Comfrey growing in undergrowth near local allotment gardens

The flower colour varies depending on the particular species. In our neighbourhood it is Russian Comfrey Symphytum x uplandicum that grows abundantly and this species bears pinkish-purple flowers in curved clusters.

Comfrey is an extremely useful herb for gardeners. The leaves are rich in plant foods and as Comfrey leaves decay quite quickly, these vital substances are then released. The leaves can be used in various ways:

as a mulch
as a lining in a potato trench
as a compost activator
to make a nutrient rich leafmould for potting compost
to make a liquid plant food

I’ve used it for most of these purposes in the past but I still collect some every year to make up a new batch of free, organic, liquid plant food. This plant food is rich in potash and has useful amounts of nitrogen and phosphate too. I find it works well on flowering plants and fruiting plants (such as tomatoes).

This rather sinister-looking liquid is my 'magic potion' plant food. — This is the remains of my Comfrey concentrate from last Summer. (Another recycled milk carton there 😉 )

Off I went into the damp undergrowth in my wellie boots – Comfrey grows best in the shady areas under some trees. I’d gone prepared in garden gloves too as the Comfrey stems can be rather rough – plus it always grows in the vicinity of Stinging Nettles so gloves are generally a good plan. (Nettle is another marvelous plant, but that’s another story.)

My armful of Comfrey stems ready to make magic. You can see how well the Soapwort has recovered now, up in its jute plant hanger on the fence.

I cut an armful of Comfrey stems which looks quite a large pile, but as I am only using the leaves I knew this would be about the right amount for what I needed. The next task was to make my Comfrey concentrate container from some recycled milk cartons (oh! those useful milk cartons again!).

When making Comfrey concentrate, the key is to pack the container as tightly as possible with shredded leaves. There is another way of making Comfrey feed by steeping the leaves in water in a bucket but I know from past experience this is rather smelly and therefore less suitable for my small backyard. So I prefer to make the concentrate and then dilute it as I need it.

I created my Comfrey concentrate container from three upcycled milk cartons. You can see the small hole that will allow the liquid to drain through into the collecting pot below.

I created my Comfrey concentrate container from three milk cartons. Two cartons were 4 pint size and the third was a 2 litre size which fitted conveniently inside one of the 4 pint cartons. I cut off the tops and handle parts of the cartons and cut a small hole, about an inch (2.5 cm) in diameter, in the base of the 2 litre carton. That’s where the liquid feed will drain through into the lower 4 pint carton.

Tearing up Comfrey leaves to pack into the container

Then it was time to begin shredding Comfrey leaves and packing them into the milk cartons, starting with the 2 litre carton first. I wasn’t cutting the leaves in any special way, just tearing them up. Some of the lower leaves are larger than my hand, around 8-9 inches (20-22 cm) long. Again, I took the precaution of wearing gloves as plant fibres can be quite tough and can easily tear through skin, if you aren’t careful.

That's one half of the container full of shredded Comfrey, now for the second half — That’s one half of the container full of shredded Comfrey, now for the second half

When the 2 litre carton was full of shredded Comfrey leaves, I then shredded the rest of the leaves from the stems I had cut and filled up the 4 pint carton too. This part was then ready to form the ‘lid’ to my Comfrey plant food concentrate container.

Time to fix together the two halves of my Comfrey concentrate container

Finally, I carefully fitted the ‘lid’ section in place and that was my Comfrey plant food concentrate prepared. Now all I need to do is wait a few weeks until the leaves break down and the rich dark brown Comfrey concentrate will be ready to feed my Sweet Peas and other plants.

My Comfrey concentrate container filled and fixed - ready to rot — My Comfrey concentrate container filled and fixed – ready to rot

When I use the Comfrey concentrate, I will add a little to 5 litres of water in the watering can when watering my plants. The recommended ratio for use is 1:10 – 1:20 according to my Encyclopedia of Organic Gardening – which I found to be an incredibly useful and practical book, when starting out in organic gardening. To use Comfrey feed on fruiting plants, such as tomatoes, the feed should be used three times a week.